Image forming apparatus with photoconductive body, and computer-readable storage medium

Abstract

An image forming apparatus forms on a photoconductive body an evaluation chart including first patterns and second patterns. In the first pattern, with respect to a row of dots formed in a main scan direction by a predetermined light beam, a row of dots formed by a next light beam is shifted in the main scan direction, and in the second pattern, with respect to the row of dots formed in the main scan direction by the predetermined light beam, the row of dots formed by the next light beam is shifted in the main scan direction but in a direction opposite to a shift direction of the first pattern. The evaluation chart includes a first pattern group which is formed by the first patterns which are repeated, and a second pattern group which is formed by the second patterns which are repeated.

What is claimed is:  
     
       1. An image forming apparatus comprising: 
       a light source portion emitting a plurality of light beams;  
       a photoconductive body having an image forming surface;  
       a deflecting unit deflecting the plurality of light beams from the light source portion to simultaneously scan the image forming surface of the photoconductive body; and  
       a controller controlling the plurality of light beams to form an evaluation chart on the image forming surface of the photoconductive body,  
       said evaluation chart including first patterns and second patterns,  
       in the first pattern, with respect to a row of dots formed in a main scan direction by a predetermined light beam, a row of dots formed by a next light beam is shifted in the main scan direction,  
       in the second pattern, with respect to the row of dots formed in the main scan direction by the predetermined light beam, the row of dots formed by the next light beam is shifted in the main scan direction but in a direction opposite to a shift direction of the first pattern,  
       said evaluation chart including a first pattern group which is formed by the first patterns which are repeated in a sub scan direction with a period that is an integer multiple of a total number of the plurality of light beams and are also repeated in the main scan direction at predetermined intervals, and a second pattern group which is formed by the second patterns which are repeated in the sub scan direction with a period that is an integer multiple of the total number of light beams and are also repeated in the main scan direction at predetermined intervals.  
     
     
       2. The image forming apparatus as claimed in  claim 1 , further comprising: 
       an output section printing the evaluation chart on the image forming surface of the photoconductive body onto a recording medium.  
     
     
       3. The image forming apparatus as claimed in  claim 2 , wherein said output section prints the evaluation chart such that, of the plurality of light beams B 1 , B 2 , . . . , Bm, where Bm≧2, the first and second pattern groups formed by the light beams B 1  and B 2 , the first and second pattern groups formed by the light beams B 2  and B 3 , . . . , the first and second pattern groups formed by the light beams B(m−1) and Bm, and the first and second pattern groups formed by the light beams Bm and B 1  are printed on a single recording medium. 
     
     
       4. The image forming apparatus as claimed in  claim 1 , wherein corresponding first and second pattern groups are arranged adjacent to each other on the evaluation chart. 
     
     
       5. The image forming apparatus as claimed in  claim 1 , wherein each first pattern group has a corresponding second pattern group arranged adjacent thereto in both the main scan direction and the sub scan direction. 
     
     
       6. The image forming apparatus as claimed in  claim 1 , wherein said controller variably controls a number of dots of the row of dots of each of the plurality of light beams when forming the evaluation chart. 
     
     
       7. The image forming apparatus as claimed in  claim 1 , wherein said controller variably controls a distance in the main scan direction between the row of dots formed by the predetermined light beam and the row of dots formed by the next light beam when forming the evaluation chart. 
     
     
       8. The image forming apparatus as claimed in  claim 1 , wherein said controller variably controls conditions related to forming the dots when forming the evaluation chart. 
     
     
       9. The image forming apparatus as claimed in  claim 1 , wherein said controller controls the plurality of light beams to form an evaluation chart having a pattern group of one of the plurality of light beams with a phase which is shifted in advance in the main scan direction, with respect to each of the first pattern group and the second pattern group. 
     
     
       10. The image forming apparatus as claimed in  claim 9 , further comprising: 
       phase correcting amount setting means for setting a phase correcting amount in the main scan direction.  
     
     
       11. An image forming apparatus comprising: 
       a light source portion emitting a plurality of light beams;  
       a photoconductive body having an image forming surface;  
       a deflecting unit deflecting the plurality of light beams from the light source portion to simultaneously scan the image forming surface of the photoconductive body; and  
       a controller controlling the plurality of light beams to form an evaluation chart on the image forming surface of the photoconductive body,  
       said evaluation chart including first patterns and second patterns,  
       in the first pattern, with respect to a row of dots formed in a main scan direction by a predetermined light beam, a row of dots formed by a next light beam is shifted in the main scan direction,  
       in the second pattern, with respect to the row of dots formed in the main scan direction by the predetermined light beam, the row of dots formed by the next light beam is shifted in the main scan direction but in a direction opposite to a shift direction of the first pattern,  
       said evaluation chart including a first pattern group which is formed by the first patterns which are repeated in a sub scan direction with a period that is an integer multiple of a total number of the plurality of light beams, and a second pattern group which is formed by the second patterns which are repeated in the sub scan direction with a period that is an integer multiple of the total number of light beams.  
     
     
       12. The image forming apparatus as claimed in  claim 11 , further comprising: 
       an output section printing the evaluation chart on the image forming surface of the photoconductive body onto a recording medium.  
     
     
       13. The image forming apparatus as claimed in  claim 11 , wherein the first and second pattern groups arranged in the sub scan direction in the evaluation chart are disposed in a scan start side of a scan range of said deflecting unit. 
     
     
       14. The image forming apparatus as claimed in  claim 11 , wherein the first and second pattern groups arranged in the sub scan direction in the evaluation chart are disposed in approximately a central portion of a scan range of said deflecting unit. 
     
     
       15. The image forming apparatus as claimed in  claim 11 , wherein said controller variably controls a number of dots of the row of dots of each of the plurality of light beams when forming the evaluation chart. 
     
     
       16. The image forming apparatus as claimed in  claim 11 , wherein said controller variably controls a distance in the main scan direction between the row of dots formed by the predetermined light beam and the row of dots formed by the next light beam when forming the evaluation chart. 
     
     
       17. The image forming apparatus as claimed in  claim 11 , wherein said controller variably controls conditions related to forming the dots when forming the evaluation chart. 
     
     
       18. The image forming apparatus as claimed in  claim 11 , wherein said controller controls the plurality of light beams to form an evaluation chart having a pattern group of one of the plurality of light beams with a phase which is shifted in advance in the main scan direction, with respect to each of the first pattern group and the second pattern group. 
     
     
       19. The image forming apparatus as claimed in  claim 18 , further comprising: 
       phase correcting amount setting means for setting a phase correcting amount in the main scan direction.  
     
     
       20. A computer-readable storage medium which stores a program for causing a computer to carry out an imaging process comprising the procedures of: 
       causing the computer to deflect a plurality of light beams to simultaneously scan an image forming surface of a photoconductive body; and  
       causing the computer to control the plurality of light beams to form an evaluation chart on the image forming surface of the photoconductive body,  
       said evaluation chart including first patterns and second patterns,  
       in the first pattern, with respect to a row of dots formed in a main scan direction by a predetermined light beam, a row of dots formed by a next light beam is shifted in the main scan direction,  
       in the second pattern, with respect to the row of dots formed in the main scan direction by the predetermined light beam, the row of dots formed by the next light beam is shifted in the main scan direction but in a direction opposite to a shift direction of the first pattern,  
       said evaluation chart including a first pattern group which is formed by the first patterns which are repeated in a sub scan direction with a period that is an integer multiple of a total number of the plurality of light beams and are also repeated in the main scan direction at predetermined intervals, and a second pattern group which is formed by the second patterns which are repeated in the sub scan direction with a period that is an integer multiple of the total number of light beams and are also repeated in the main scan direction at predetermined intervals.  
     
     
       21. A computer-readable storage medium which stores a program for causing a computer to carry out an imaging process comprising the procedures of: 
       causing the computer to deflect a plurality of light beams to simultaneously scan an image forming surface of a photoconductive body; and  
       causing the computer to control the plurality of light beams to form an evaluation chart on the image forming surface of the photoconductive body,  
       said evaluation chart including first patterns and second patterns,  
       in the first pattern, with respect to a row of dots formed in a main scan direction by a predetermined light beam, a row of dots formed by a next light beam is shifted in the main scan direction,  
       in the second pattern, with respect to the row of dots formed in the main scan direction by the predetermined light beam, the row of dots formed by the next light beam is shifted in the main scan direction but in a direction opposite to a shift direction of the first pattern,  
       said evaluation chart including a first pattern group which is formed by the first patterns which are repeated in a sub scan direction with a period that is an integer multiple of a total number of the plurality of light beams, and a second pattern group which is formed by the second patterns which are repeated in the sub scan direction with a period that is an integer multiple of the total number of light beams.